Facial recognition systems are well known. The use of infra-red illumination to assist the capture images for the facial recognition systems is less prevalent. Most facial recognition systems work in environments with adequate conventional lighting, such as in an airport. However, an infra-red illumination system for a facial-recognition system may be useful in venues that do not have enough ambient lighting to support adequate capture of images. As an example, casinos and bars tend to be relatively dark environments. Installing adequate conventional lighting is often not feasible and may be undesirable as being unsuitable to the desired ambiance.
One problem with infra-red illumination is that it loses some of the potential data that might be used to make a facial recognition match due, in part, to the fact that the captured image is essentially monochromatic. Another problem with infra-red illumination is that when it is shined in a person's eyes it does not cause a dilated pupil to contract. Even though infra-red light is not as inherently harmful as visible light (because of its longer wavelength) more of it will reach the retina due if the pupil is dilated. This effect is further exacerbated by a dark environment such as a bar where a person's eyes are generally more dilated.
This problem is not usually of concern with facial recognition systems because the designers of such systems, which are mainly oriented towards surveillance, do not expect: (a) the user to have a long or continuous exposure to the illumination; or (b) the user to be staring directly at the source of the illumination. However, if one is to use a facial recognition system with a persistent infrared (IR) light source it may be useful to find ways to mitigate the possibility of over-exposure to such IR light.
One type of system which uses IR illumination is a system which tracks gazes, e.g. the movement of the human eye. For example, one type of system uses an IR gaze tracking system to assist handicapped persons in their use of computers by tracking their eye movements. Such systems require the user to spend long periods with IR illumination exposure.
It is believed that the risks due to IR illumination exposure of this type are small with point sources of IR light used within a well-lit room. However, the effects of long-term exposure to of multiple sources of IR light in dimly lit rooms are not well documented.